The objectives of this proposal are kinetic investigations of the enzyme delta4-3-keto-steroid-5alpha-oxidoreductase obtained from the rat ventral prostate and the androgen dependent Dunning R3327 adenocarcinoma of prostatic origin. The proposed studies include the preparation of hormone analogs as probes of the substrate specificity of the 5alpha reductase derived from the normal and transformed tissues. Further investigations include the preparation of active-site generated irreversible inhibitors of the reductase as metabolic blockers of the biosynthesis of dihydrotestosterone.